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Journal articleAbdalla A, Abe M, Abend S, et al., 2025,
Terrestrial Very-Long-Baseline Atom Interferometry: summary of the second workshop
, EPJ Quantum Technology, Vol: 12This summary of the second Terrestrial Very-Long-Baseline Atom Interferometry (TVLBAI) Workshop provides a comprehensive overview of our meeting held in London in April 2024 (Second Terrestrial Very-Long-Baseline Atom Interferometry Workshop, Imperial College, April 2024), building on the initial discussions during the inaugural workshop held at CERN in March 2023 (First Terrestrial Very-Long-Baseline Atom Interferometry Workshop, CERN, March 2023). Like the summary of the first workshop (Abend et al. in AVS Quantum Sci. 6:024701, 2024), this document records a critical milestone for the international atom interferometry community. It documents our concerted efforts to evaluate progress, address emerging challenges, and refine strategic directions for future large-scale atom interferometry projects. Our commitment to collaboration is manifested by the integration of diverse expertise and the coordination of international resources, all aimed at advancing the frontiers of atom interferometry physics and technology, as set out in a Memorandum of Understanding signed by over 50 institutions (Memorandum of Understanding for the Terrestrial Very Long Baseline Atom Interferometer Study).
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Journal articleBennett S, Hanany A, Kumaran G, et al., 2025,
Quiver subtraction on the Higgs branch
, Nuclear Physics B, Vol: 1016, ISSN: 0550-3213This paper classifies all Higgs branch Higgsing patterns for simply-laced unitary quiver gauge theories with eight supercharges (including multiple loops) and introduces a Higgs branch subtraction algorithm. All possible minimal transitions are given, identifying differences between slices that emerge on the Higgs and Coulomb branches. In particular, the algorithm is sensitive to global information including monodromies and Namikawa-Weyl groups. Guided by symplectic duality, the algorithm further determines the global symmetry on the Coulomb branch, and verifies the exclusion of C type or F<inf>4</inf> global symmetry for (simply-laced) unitary quiver gauge theories. The Higgs branches of some unitary quivers are verified to give slices in the nilpotent cones of exceptional simple Lie algebras.
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Journal articleIsichei R, Magueijo J, 2025,
Attractive voids
, International Journal of Modern Physics D, ISSN: 0218-2718 -
Journal articleAlvey J, Bhardwaj U, Domcke V, et al., 2025,
Leveraging time-dependent instrumental noise for the LISA stochastic gravitational wave background analysis
, Physical Review D, Vol: 111, ISSN: 2470-0010Variations in the instrumental noise of the Laser Interferometer Space Antenna (LISA) over time are expected as a result of, e.g., scheduled satellite operations or unscheduled glitches. We demonstrate that these fluctuations can be leveraged to improve the sensitivity to stochastic gravitational wave backgrounds (SGWBs) compared to the stationary noise scenario. This requires optimal use of data segments with downward noise fluctuations, and thus a data analysis pipeline capable of analyzing and combining shorter time segments of mission data. We propose that simulation based inference is well suited for this challenge. In an approximate, but state-of-the-art, modeling setup, we show by comparison with Fisher information matrix estimates that the optimal information gain can be achieved in practice.
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Journal articleBassani PM, Magueijo J, 2025,
How to make a universe
, Physical Review D, Vol: 111, ISSN: 2470-0010We establish the general conditions under which evolution in the laws of physics leads to violations of the conservation of the energy-momentum tensor for matter, resulting in matter creation or destruction. They make use of global time variables canonically dual to the constants of nature. Such times flow at a rate determined by what can be interpret as the chemical potential of the fundamental constants (in analogy with phenomenological clocks based on isentropic fluids). The general condition for violations of energy conservation is then that a matter parameter evolves as a function of a gravity clock or vice versa. This framework can be envisaged as the environment within which a natural selection scenario operates, powered by random mutations in the values of the constants of nature (or indeed any other variability in the laws in terms of the times defined above). The prize function is the creation of matter, followed by its preservation. This can be accomplished in an environment where diffeomorphism invariance is among the possible theories, with mutations modeled, for example, on the absorbing Markov chain. In such a setup, the diffeormorphism invariant state with fixed constants (or any nearby state) should be the absorbing state. John Wheeler's "higgledy-piggledy"chaotic cosmic start therefore finds a realization in this model, where its own demise and the establishment of order and seemingly immutable laws is also a prediction of the model.
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Journal articleWebb JK, Lee CC, Milaković D, et al., 2025,
The mystery of alpha and the isotopes
, Monthly Notices of the Royal Astronomical Society Letters, Vol: 539, Pages: L1-L6We report unbiased Artificial Intelligence (AI) measurements of the fine structure constant α in two proximate absorption regions in the spectrum of the quasar HE0515−4414. The data are high resolution, high signal to noise, and laser frequency comb calibrated, obtained using the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectrograph on the VLT. The high quality of the data and proximity of the regions motivate a differential comparison, exploring the possibility of spatial variations of fundamental constants, as predicted in some theories. We show that if the magnesium isotopic relative abundances are terrestrial, the fine structure constants in these two systems differ at the 7σ level. A 3σ discrepancy between the two measurements persists even for the extreme non-terrestrial case of 100 per cent <sup>24</sup>Mg, if shared by both systems. However, if Mg isotopic abundances take independent values in these two proximate systems, one terrestrial, the other with no heavy isotopes, both can be reconciled with a terrestrial α , and the discrepancy between the two measurements falls to 2σ. We cannot rule out other systematics that are unaccounted for in our study that could masquerade as a varying alpha signal. We discuss varying constant and varying isotope interpretations and resolutions to this conundrum for future high precision measurements.
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Journal articleGarbrecht B, Ghoderao PS, Rajantie A, 2025,
Curvature perturbations from vacuum transition during inflation
, Journal of Cosmology and Astroparticle Physics, Vol: 2025We demonstrate that in the presence of a light scalar spectator field, vacuum transitions taking place during inflation can produce large, potentially detectable non-Gaussian signatures in the primordial curvature perturbation. Such transitions are common in theories with multiple scalar fields when the potential has several minima. Our computation proceeds by numerically finding the instanton solution that describes quantum tunnelling between vacuum states in a de Sitter background, calculating its dependence on the spectator field and, thereby, its effect on the expansion of space. For a scenario with Higgs inflation, we obtain the non-Gaussianity parameter fNL ∼ O(10) and study its parameter dependence.
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Journal articleBeccaria M, Kurlyand SA, Tseytlin AA, 2025,
On non-planar ABJM anomalous dimensions from M2 branes in AdS4 × S7/ℤk
, Journal of High Energy Physics, Vol: 2025Planar parts of conformal dimensions of primary operators in U<inf>k</inf>(N) × U<inf>−k</inf>(N) ABJM theory are controlled by integrability. Strong coupling asymptotics of planar dimensions of operators with large spins can be found from the energy of semiclassical strings in AdS<inf>4</inf> × CP<sup>3</sup> but computing non-planar corrections requires understanding higher genus string corrections. As was pointed out in arXiv:2408.10070, there is an alternative way to find the non-planar corrections by quantizing M2 branes in AdS<inf>4</inf> × S<sup>7</sup>/ℤ<inf>k</inf> which are wrapped around the 11d circle of radius 1/k = λ/N and generalize spinning strings in AdS<inf>4</inf> × CP<sup>3</sup>. Computing the 1-loop correction to the energy of M2 brane that corresponds to the long folded string with large spin S in AdS<inf>4</inf> allowed to obtain a prediction for the large λ limit of non-planar corrections to the cusp anomalous dimension. Similar predictions were found for non-planar dimensions of operators dual to M2 branes that generalize the “short” and “long” circular strings with two equal spins J<inf>1</inf> = J<inf>2</inf> in CP<sup>3</sup>. Here we consider two more non-trivial examples of 1-loop M2 brane computations that correspond to: (i) long folded string with large spin S in AdS<inf>4</inf> and orbital momentum J in CP<sup>3</sup> whose energy determines the generalized cusp anomalous dimension, and (ii) circular string with spin S in AdS<inf>4</inf> and spin J in CP<sup>3</sup>. We find the leading terms of the expansion of the corresponding 1-loop M2 brane energies in 1/k. We also discuss similar semiclassical 1-loop M2 brane computation in flat 11d background and comment on p
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Journal articleGammal JE, Ghaleb A, Franciolini G, et al., 2025,
Reconstructing primordial curvature perturbations via scalar-induced gravitational waves with LISA
, Journal of Cosmology and Astroparticle Physics, Vol: 2025Many early universe scenarios predict an enhancement of scalar perturbations at scales currently unconstrained by cosmological probes. These perturbations source gravitational waves (GWs) at second order in perturbation theory, leading to a scalar-induced gravitational wave (SIGW) background. The LISA detector, sensitive to mHz GWs, will be able to constrain curvature perturbations in a new window corresponding to scales k ∈ [10<sup>10</sup>, 10<sup>14</sup>] Mpc<sup>-1</sup>, difficult to probe otherwise. In this work, we forecast the capabilities of LISA to constrain the source of SIGWs using different approaches: i) agnostic, where the spectrum of curvature perturbations is binned in frequency space; ii) template-based, modeling the curvature power spectrum based on motivated classes of models; iii) ab initio, starting from first-principles model of inflation featuring an ultra-slow roll phase. We compare the strengths and weaknesses of each approach. We also discuss the impact on the SIGW spectrum of non-standard thermal histories affecting the kernels of SIGW emission and non-Gaussianity in the statistics of the curvature perturbations. Finally, we propose simple tests to assess whether the signal is compatible with the SIGW hypothesis. The pipeline used is built into the SIGWAY code.
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Journal articleBlanco-Pillado JJ, Cui Y, Kuroyanagi S, et al., 2025,
Gravitational waves from cosmic strings in LISA: reconstruction pipeline and physics interpretation
, Journal of Cosmology and Astroparticle Physics, Vol: 2025We initiate the LISA template databank for stochastic gravitational wave backgrounds sourced by cosmic strings. We include two templates, an analytical template, which enables more flexible searches, and a numerical template derived directly from large Nambu-Goto simulations of string networks. Using searches based on these templates, we forecast the parameter space within the reach of the experiment and the precision with which their parameters will be reconstructed, provided a signal is observed. The reconstruction permits probing the Hubble expansion and new relativistic DoF in the early universe. We quantify the impact that astrophysical foregrounds can have on these searches. Finally, we discuss the impact that these observations would have on our understanding of the fundamental models behind the string networks. Overall, we prove that LISA has great potential for probing cosmic string models and may reach tensions as low as Gμ = 10<sup>-16</sup> - 10<sup>-17</sup>, which translates into energy scales of the order 10<sup>11</sup> GeV.
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Journal articleChen CYR, Joung E, Mkrtchyan K, et al., 2025,
Higher-order chiral scalar from boundary reduction of 3d higher-spin gravity
, Journal of High Energy Physics, Vol: 2025We use a recently proposed covariant procedure to reduce the Chern-Simons action of three-dimensional higher-spin gravity to the boundary, resulting in a Lorentz covariant action for higher-order chiral scalars. After gauge-fixing, we obtain a higher-derivative action generalizing the s = 1 Floreanini-Jackiw and s = 2 Alekseev-Shatashvili actions to arbitrary spin s. For simplicity, we treat the case of general spin at the linearized level, while the full non-linear asymptotic boundary conditions are presented in component form for the SL(3, ℝ) case. Finally, we extend the spin-3 linearized analysis to a background with non-trivial higher-spin charge and show that it has a richer structure of zero modes.
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Journal articleMagueijo J, Manchanda GS, 2025,
Quantum wormholes at spatial infinity
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 864, ISSN: 0370-2693We derive the interesting result that the two asymptotically flat Universes classically linked by the Einstein-Rosen bridge may also be quantum mechanically connected in their far out regions. This would be felt by the Newtonian potential far away from a black/white hole system, and raises the possibility of establishing communication via perturbations. We obtain our results by means of wavepackets with a small variance in the mass, solving the equations derived from a maximally symmetry-reduced canonical quantisation method. Mass and a proxy of the Newtonian potential appear as canonical duals, leading to a Heisenberg uncertainty relation between the two. Coherent states are then built, which become non-semiclassical only in two regions: asymptotic spatial infinity (where unitarity forces the packets to “feel” the other asymptotic spatial infinity), and inside the horizon at r=Gm where there is ringing. Whilst the latter has been noted in the literature, the former—the quantum wormhole at spatial infinity—seems to have eluded past scrutiny. Even under a coherent state there is a free parameter determining the distance beyond which the states becomes non-semiclassical, given the ambiguity in defining quadratures and squeezing, with departures eventually becoming of order one and cutting off the Newtonian potential. Further studies are required to examine the stability of these conclusions beyond their symmetry-reduced test tube.
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Journal articleBeccaria M, Tseytlin AA, 2025,
Non-planar corrections to ABJM Bremsstrahlung function from quantum M2 brane
, Journal of Physics A Mathematical and Theoretical, Vol: 58, ISSN: 1751-8113As was shown in Giombi and Tseytlin (2023 Phys. Rev. Lett. 130 201601), the leading large N, fixed k correction in the localization result for the expectation value of the 1/2 BPS circular Wilson loop in U (N)<inf>k</inf> × U (N)<inf>−k</inf> ABJM theory given by the (sin 2π/k)<sup>−1</sup> factor can be reproduced on the dual M-theory side as the one-loop correction in the partition function of M2 brane in AdS<inf>4</inf>×S<sup>7</sup>/ℤ<inf>k</inf> with AdS<inf>2</inf>×S<sup>1</sup> world volume. Here we prove, following the suggestion in Giombi et al (2024 J. High Energy Phys. JHEP11(2024)056), that the analogous fact is true also for the corresponding correction B<inf>1</inf> = − 1/2π k cot 2π/k in the localization result for the Bremsstrahlung function associated with the Wilson loop with a small cusp in either AdS<inf>4</inf> or CP<sup>3</sup>. The corresponding M2 brane is wrapped on the 11d circle and generalizes the type IIA string solution in AdS<inf>4</inf>×CP<sup>3</sup> ending on the cusped line. We show that the one-loop term in the M2 brane partition function reproduces the localization expression for B<inf>1</inf> as the coefficient of the leading term in its small cusp expansion.
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Journal articleDepta PF, Domcke V, Franciolini G, et al., 2025,
Pulsar timing array sensitivity to anisotropies in the gravitational wave background
, Physical Review D, Vol: 111, ISSN: 2470-0010Pulsar timing array (PTA) observations have recently gathered substantial evidence for the existence of a gravitational wave background in the nHz frequency band. Searching for anisotropies in this signal is key to determining its origin and in particular to distinguish possible astrophysical from cosmological sources. In this work, we assess the sensitivity of current and future pulsar timing arrays to such anisotropies using the full covariance matrix of pulsar timing delays. While current day pulsar timing arrays can only set mildly informative constraints on the dipole and quadrupole, we show that percent-level accuracy for several low multipoles can be achieved in the near future. Moreover, we demonstrate that anisotropies in the gravitational wave background and the Hellings-Downs angular correlation, indicating the presence of gravitational waves, are approximately uncorrelated and can hence be reconstructed independently. These results can be reproduced with fastpta, a publicly available python code to forecast the constraining power of PTA configurations.
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Journal articleHull C, Hutt ML, Lindström U, 2025,
Generalised symmetries in linear gravity
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>Linearised gravity has a global symmetry under which the graviton is shifted by a symmetric tensor satisfying a certain flatness condition. There is also a dual symmetry that can be associated with a global shift symmetry of the dual graviton theory. The corresponding conserved charges are shown to satisfy a centrally-extended algebra. We discuss the gauging of these global symmetries, finding an obstruction to the simultaneous gauging of both symmetries which we interpret as a mixed ’t Hooft anomaly for the ungauged theory. We discuss the implications of this, analogous to those resulting from a similar structure in Maxwell theory, and interpret the graviton and dual graviton as Nambu-Goldstone modes for these shift symmetries.</jats:p>
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Journal articleHo M, Price H, Evans T, et al., 2025,
Enhancing foresight models with network science: measuring innovation feedbacks within the Chain-Linked Model
, Technological Forecasting and Social Change, Vol: 213, ISSN: 0040-1625A granular understanding of innovation dynamics is crucial for forecasting how and when different actors within the innovation system can make valuable contributions. Existing theoretical foundations of the foresight practice are largely qualitative and often oversimplify the innovation process. While foresight practitioners acknowledge the existence of knowledge feedback loops, these feedback loops are rarely quantified systematically in empirical forecasting studies. Innovators and funders tend to choose their dyadic relationships but rarely have visibility over the wider, dynamic innovation network. This study enriches innovation theories for the foresight practice by leveraging multilayer citation networks to explore innovation translation pathways, achieved by integrating data from market entries, clinical trials, patents, publications, funders, and grants over a 70-year period. Our analysis shows shifts in the order, prevalence, and tipping points of translation activities as technologies mature, with granularity not described in previous studies. We also examine the distinct funding patterns of major public and private entities throughout this maturation process, revealing their unique contributions and enriching sociotechnical explanations of innovation processes. This study improves the explainability of technology forecasting through innovation theories by reconstructing micro-technical innovation dynamics from first principles.
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Journal articleHull C, 2025,
Coupling self-dual p-form Gauge fields to self-dual branes
, Journal of Physics A Mathematical and Theoretical, Vol: 58, ISSN: 1751-8113In d = 4 k + 2 dimensions, p-form gauge fields (with p = 2 k ) with self-dual field strengths couple naturally to dyonic branes with equal electric and magnetic charges. Sen’s action for a p-form gauge field with self-dual field strength coupled to a spacetime metric g involves an explicit Minkowski metric; however, this action can be generalised to provide a theory in which the Minkowski metric is replaced by a second metric g ¯ on spacetime. This theory describes a physical sector, consisting of the chiral p-form gauge field coupled to the dynamical metric g, plus an auxiliary sector consisting of a second chiral p-form and the second metric g ¯ . The fields in this auxiliary sector only couple to each other and have no interactions with the physical sector. However, in this theory, the standard coupling to a brane given by integrating the gauge potential over the world-volume of the brane is problematic as the physical gauge potential depends non-locally on the fields appearing in the action. A consistent coupling is given by introducing Dirac branes (generalising Dirac strings), and is shown to have generalised symmetries corresponding to invariance under deforming the positions of the Dirac branes, provided the Dirac branes do not intersect any physical brane world-volumes.
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Journal articleAkhond M, Arias-Tamargo G, Carta F, et al., 2025,
On brane systems with O+ planes — 5d and 6d SCFTs
, Journal of High Energy Physics, Vol: 2025We study Higgs branches of field theories with 8 supercharges in 5 and 6 dimensions, focusing on theories realised on 5-brane webs in Type IIB with an O7<sup>+</sup> plane, or a D6-D8-NS5 brane system in Type IIA in the presence of an O8<sup>+</sup> plane. We find magnetic quivers for the Higgs branches of these theories. The main consequence of the presence of the orientifold is that it renders the magnetic quiver to be non-simply-laced. We propose a contribution of the O7<sup>+</sup> to the usual stable intersection number of 5-branes from tropical geometry, and show that it is consistent with Fayet-Iliopoulos deformations of magnetic quivers which represent mass deformations of 5d SQFTs. From the magnetic quivers, we compute phase diagrams and highest weight generating functions for the Higgs branches, enabling us to identify the global form of the flavour symmetry for several families of 5d SQFTs; among them Bhardwaj’s rank-1 theory. For 6d theories realised on a −4 curve, we observe the appearance of an additional D<inf>4</inf> slice on top of the phase diagram as one goes to the tensionless limit.
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Journal articleLin J, Skrzypek T, Stelle KS, 2025,
Compactification on Calabi-Yau threefolds: consistent truncation to pure supergravity
, Journal of High Energy Physics, Vol: 2025We study compactifications of eleven- and ten-dimensional maximal supergravity on Calabi-Yau threefolds. We explicitly construct truncations to pure supergravity with eight supercharges in five and four dimensions and show that they are consistent, i.e. that every solution of the lower-dimensional equations of motion fully solves the higher-dimensional ones. We furthermore match the supersymmetry transformations and demonstrate the consistency to full non-linear order in fermions. Our construction is independent of the choice of Calabi-Yau threefold and only involves the universal structures such as the Kähler form and the holomorphic three-form, in agreement with implicit constructions in the generalised geometry literature. As an immediate application, we embed four-dimensional extremal black holes in the higher-dimensional supergravities. We furthermore propose Ansätze for consistent truncations on all universal structures, leading to supergravities with additional matter multiples. An extensive list of equations of motion and supersymmetry transformations for various supergravity theories is provided in the appendix.
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Journal articleAcharya B, Alexandre J, Benes P, et al., 2025,
Search for Highly Ionizing Particles in pp Collisions during LHC Run 2 Using the Full MoEDAL Detector.
, Phys Rev Lett, Vol: 134This search for magnetic monopoles (MMs) and high electric charge objects (HECOs) with spins 0, 1/2, and 1, uses for the first time the full MoEDAL detector, exposed to 6.46 fb^{-1} proton-proton collisions at 13 TeV. The results are interpreted in terms of Drell-Yan and photon-fusion pair production. Mass limits on direct production of MMs of up to 10 Dirac magnetic charges and HECOs with electric charge in the range 10e to 400e, were achieved. The charge limits placed on MM and HECO production are currently the strongest in the world. MoEDAL is the only LHC experiment capable of being directly calibrated for highly ionizing particles using heavy ions and with a detector system dedicated to definitively measuring magnetic charge.
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Journal articleBenetti Genolini P, Gauntlett JP, Jiao Y, et al., 2025,
Toric gravitational instantons in gauged supergravity
, Physical Review D, Vol: 111, ISSN: 2470-0010We introduce a general class of toric gravitational instantons in D=4, N=2 gauged supergravity, namely Euclidean supersymmetric solutions with U(1)2 isometry. Such solutions are specified by a "supergravity labeled polytope,"where the labels encode the four-manifold topology, the choice of magnetic fluxes, and certain signs associated with the Killing spinor. Equivariant localization allows us to write down the gravitational free energy for such a solution, assuming it exists, and study its properties. These results open the way for a systematic study of holography in this setting, where the dual large N field theories are defined on the boundary three-manifolds, which are (squashed) lens spaces L(p,q) or generalizations with orbifold singularities.
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Journal articleFranco S, Hanany A, He YH, et al., 2025,
Duality walls, duality trees and fractional branes
, International Journal of Modern Physics A, Vol: 40, ISSN: 0217-751XIn this paper, we compute the NSVZ beta functions for =1 four-dimensional quiver theories arising from D-brane probes on singularities, complete with anomalous dimensions, for a large set of phases in the corresponding duality tree. While these beta functions are zero for D-brane probes, they are nonzero in the presence of fractional branes. As a result there is a nontrivial RG behavior. We apply this running of gauge couplings to some toric singularities such as the cones over Hirzebruch and del Pezzo surfaces. We observe the emergence in string theory, of "Duality Walls,"a finite energy scale at which the number of degrees of freedom becomes infinite and beyond which Seiberg duality does not proceed. We also identify certain quiver symmetries as T-duality-like actions in the dual holographic theory.
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Journal articleDuff MJ, 2025,
Montonen-Olive duality of gauged supergravity?
, Journal of Physics A Mathematical and Theoretical, Vol: 58, ISSN: 1751-8113The vanishing of the SO(N) β-function of gauged N > 4 supergravity has long seemed like an answer looking for a question. Here we conjecture that it is a consequence of a Montonen-Olive style electric/magnetic duality.
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Journal articleChen CYR, De Rham C, Tolley AJ, 2025,
Deformations of extremal black holes and the UV
, Physical Review D, Vol: 111, ISSN: 2470-0010It has recently been noted that deformations of extremal anti-de Sitter (AdS) black holes in four and higher dimensions are generically nonsmooth or singular on the horizon. Further, it was found that certain deformations of asymptotically flat extremal black holes are marginal, causing the nature of the horizon to be strongly sensitive to UV corrections - in particular, Wilson coefficients associated with consistent UV completions generically lead to worse behavior on the horizon. In this work, we extend the discussion of deformed horizons in the presence of UV corrections to extremal charged black holes in AdS, where we find a tower of marginal perturbations for different black hole masses. We argue that the apparent UV sensitivity of marginal modes is, in fact, a feature of the UV theory, which is correctly reproduced by the effective field theory (EFT), and illustrate this with explicit UV completions confirming the validity of the EFT. We demonstrate that the same holds for a scalar-Maxwell EFT with known UV completion. In the gravitational case, the sign of EFT corrections to marginal perturbations is generally connected with the signs implied by positivity bounds, with UV completions generically leading to worse behavior on the horizon. We conjecture that this result is more generic and use this to derive more general positivity bounds motivated by the weak gravity conjecture, which we illustrate with further evidence.
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Journal articleChen CYR, Margalit A, De Rham C, et al., 2025,
Causality in the presence of stacked shockwaves
, Physical Review D, Vol: 111, ISSN: 2470-0010Relativistic causality constrains the S-matrix both through its analyticity, and by imposing lower bounds on the scattering time delay. These bounds are easiest to determine for spacetimes which admit either a timelike or null Killing vector. We revisit a class of pp-wave spacetimes and carefully determine the scattering time delay for arbitrary incoming states in the eikonal, semiclassical, and Born approximations. We apply this to the effective field theory of gravity in arbitrary dimensions. It is well-known that higher-dimension operators such as the Gauss-Bonnet term, when treated perturbatively at low energies, can appear to make both positive and negative contributions to the time delays of the background geometry. We show that even when multiple shockwaves are stacked, the corrections to the scattering time delay relative to the background are generically unresolvable within the regime of validity of the effective field theory so long as the Wilson coefficients are of order unity. Phrased the other way, this can be read as a bound on the Wilson coefficient from infrared causality which are consistent with positivity/bootstrap bounds.
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Journal articleTagliazucchi M, Braglia M, Finelli F, et al., 2025,
Quest for CMB spectral distortions to probe the scalar-induced gravitational wave background interpretation of pulsar timing array data
, Physical Review D, Vol: 111, ISSN: 2470-0010Gravitational waves (GW) sourced by second-order primordial curvature fluctuations are among the favored models fitting the recent pulsar timing array (PTA) measurement of a stochastic GW background (SGWB). We study how spectral distortions (SDs) and anisotropies of the cosmic microwave background (CMB) can constrain such scalar fluctuations. Whereas COBE FIRAS data have no sufficient sensitivity to probe the PTA log-normal hypothesis, we show how future PIXIE-like experiments can detect the CMB SDs from the scalar-induced interpretation of the SGWB in PTA data. We finally show how the transformative synergy between PTA data and future CMB SD measurements is important for reconstructing primordial fluctuations at these small scales.
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Journal articleHull C, Lindström U, Velásquez Cotini Hutt ML, 2025,
Gauge-invariant charges of the dual graviton
, Journal of High Energy Physics, Vol: 2025The free graviton theory given by linearising Einstein’s theory has a dual formulation in terms of a dual graviton field. The dual graviton theory has two gauge invariances giving rise to two conserved charges, while the ADM charges of the graviton theory become magnetic charges for the dual graviton theory. These charges can be ill-defined in topologically non-trivial settings and we find improvement terms that can be added to these to give gauge-invariant conserved charges. These gauge-invariant charges, which have local expressions in both the graviton and dual graviton formulation, give topological operators of the theory that should be considered as the generators of the genuine symmetries of the theory.
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Journal articleBuscicchio R, Torrado J, Caprini C, et al., 2025,
Stellar-mass black-hole binaries in LISA: characteristics and complementarity with current-generation interferometers
, Journal of Cosmology and Astroparticle Physics, Vol: 2025Stellar-mass black-hole binaries are the most numerous gravitational-wave sources observed to date. Their properties make them suitable for observation both by ground- and space-based detectors. Starting from synthetic catalogues constructed based on observational constraints from ground-based detectors, we explore the detection rates and the characteristic parameters of the stellar-mass black-hole binaries observable by LISA during their inspiral, using signal-to-noise ratio thresholds as a detection criterion. We find that only a handful of these sources will be detectable with signal-to-noise ratio larger than 8: about 5 sources on average in 4 years of mission duration, among which only one or two are multiband ones (i.e. merging in less than 15 years). We find that detectable sources have chirp mass 10 M <inf>⊙</inf> ≲ M<inf>c</inf> ≲ 100 M <inf>⊙</inf>, residual time-to-coalescence 4 yr ≲ τ<inf>c</inf> ≲ 100 yr, and redshift z ≲ 0.1, much closer than those observed up to now by ground-based detectors. We also explore correlations between the number of LISA detectable sources and the parameters of the population, suggesting that a joint measurement with the stochastic signal might be informative of the population characteristics. By performing parameter estimation on a subset of sources from the catalogues, we conclude that, even if LISA measurements will not be directly informative on the population due to the low number of resolvable sources, it will characterise a few, low-redshift candidates with great precision. Furthermore, we construct for the first time the LISA waterfall plot for low chirp-mass systems, as a function of their time to coalescence and inclination. We demonstrate that LISA will also be able to discriminate and characterize, through very precise parameter estimation, a population of binaries with higher masses, M<inf>c</inf> ∼ Ó(10<sup>3</sup>) M <inf
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Journal articleHull C, Hutt ML, Lindström U, 2025,
Gauging generalised symmetries in linear gravity
, Journal of High Energy Physics, Vol: 2025The theory of a free spin-2 field on Minkowski spacetime has 1-form and (d − 3)-form symmetries associated with conserved currents formed by contractions of the linearised Riemann tensor with conformal Killing-Yano 2-forms. We show that a subset of these can be interpreted as Noether currents for specific shift symmetries of the graviton that involve a Killing vector and a closed 1-form parameter. We give a systematic method to gauge these 1-form symmetries by coupling the currents to background gauge fields and introducing a particular set of counter-terms involving the background fields. The simultaneous gauging of certain pairs of 1-form and (d − 3)-form symmetries is obstructed by the presence of mixed ’t Hooft anomalies. The anomalous pairs of symmetries are those which are related by gravitational duality. The implications of these anomalies are discussed.
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Journal articleBeccaria M, Casarin L, Tseytlin AA, 2025,
Semiclassical quantization of M5 brane probes wrapped on AdS3× S3 and defect anomalies
, Journal of High Energy Physics, Vol: 2025We consider two supersymmetric M5 brane probe solutions in AdS<inf>7</inf> × S<sup>4</sup> and one in AdS<inf>4</inf> × S<sup>7</sup> that all have the AdS<inf>3</inf> × S<sup>3</sup> world-volume geometry. The values of the classical action of the first two M5 probes (with S<sup>3</sup> in AdS<inf>7</inf> or in S<sup>4</sup>) are related to the leading N<sup>2</sup> parts in the anomaly b-coefficient in the (2,0) theory corresponding to a spherical surface defect in symmetric or antisymmetric SU(N) representations. We present a detailed computation of the corresponding one-loop M5 brane partition functions finding that they vanish (in a particular regularization). This implies the vanishing of the order N<sup>0</sup> part in the b-anomaly coefficients, in agreement with earlier predictions for their exact values. It remains, however, a puzzle of how to reproduce the non-vanishing order N terms in these coefficients within the semiclassical M5-brane probe setup.
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